The Shop > Tools
Real Bull Mini-lathe Speed Controller Woes
John Rudd:
Ross,
What voltage do you read between points P1 and p3? Post this value plz.....
Your dvm needs to be set to read DC volts.....
Ross:
--- Quote from: John Rudd on September 07, 2015, 12:46:29 PM ---Ross,
What voltage do you read between points P1 and p3? Post this value plz.....
Your dvm needs to be set to read DC volts.....
--- End quote ---
Points p1-3 on the board or pot? I ran the last test on the pot
John Rudd:
The connections on the board with the potentiometer disconnected.
Disconnect the motor too.....
Just a step back or two......the lamp that blew what voltage was it?
Perhaps I should have stated it needs to be a mains 240 bulb......, :doh:Hope it wasnt any old car bulb...
Btw, I notice youre in Lincoln.....do you live anywhere near the A15/Outer Circle Drive? Ill be visiting my son on Friday, I could come over and have a look with you....
Ross:
Ok between P 1-3 is 19volts
The bulb was of unknown voltage! Obviously not enough! Just Tried a proper bulb and it gets ever so slightly brighter but does not go out even with the pot off. Surely it's got to be the potentiometer?
I am 15 miles south of Lincoln a bit off the beat and track!
John Rudd:
19 volts is too high....it should be a maximum of 12v.....
The low level control circuits are supplied by rectified mains, then there is a 22 v zener diode clamping the supply, then there is a 12 v zener diode further down stream fed by a 1.5 k resistor...This 12v supply is used to supply the juice for the speed control pot....
So, place your meter on volts dc across connection I2 (which is a ground ) and the cathode end of Z1...( the cathode end is denoted by a coloured band ) if you get the wrong end of the zener the meter will read zero...so try the other end.....you should read 12v...if its more then the zener diode is phut....
You can check the speed pot with your meter of the ohms range ( set to 20k ) connect one lead to the centre tag and the other lead to one of the outer tags,turn the spindle and watch the meter reading....should go from zero to either 5k or 10 k depending on the value of the pot, I forget it at the moment -:(
If all this gets too mich for you, you could send me the board, l'll test it and repair as required....
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